Schedule-based workflows help you save money on process instrument maintenance

It is common for work orders for a single maintenance activity to be assigned to an instrumentation technician. Once the task is complete, the technician returns to the instrument room to fill out the paperwork and record the results before assigning the next task. With plan-based maintenance, multiple tasks and work orders can be assigned to technicians. This approach reduces the time spent traveling to and from the instrument room and can reduce instrument maintenance costs by 40 % or more.

With the volatility of raw material prices, industries are challenged to adapt to the times and profit margins. In fact, one of the few ways to control costs in all industries is to be streamlined and efficient.

One of the best ways to control costs is to understand the waste that occurs in the process.

From an instrumentation perspective, this means a lot of fine-tuning to ensure that the temperatures and pressures obtained are just right for high-quality production and efficient use of inputs.

Calibrating equipment improves optimization and quality – also for other industries, whether chemical, nuclear, pharmaceutical, or pulp and paper.

Process manufacturing plants require hundreds, if not thousands, of advanced equipment to perform countless critical operations uninterruptedly, accurately, and reliably. These devices, in turn, require regular inspection, testing, calibration, and repair.

Hundreds of years of industry experience have recognized the value of documenting the details of inspection, testing, calibration, and repair described above. It's not just best practice in the industry, businesses and governments often require very clear and specific records to ensure that customers get the full value and that the health and safety of citizens are protected.

However, traditional testing, calibration, and archiving practices are also labor-intensive, and combined with talent shortages, downsized teams sometimes choose to postpone regular calibrations.

The latest industry research shows that smaller teams are able to perform and document equipment calibration at a lower overall cost, increasing productivity and reliability.

Calibration is usually performed at the location where the equipment is located (on-site calibration) or in the instrument shop.

The vast majority of field instruments consist of two parts: the basic components and the transmitter.

The basic components include flow tubes, orifice plates, pressure sensors, wet chemical sensors such as pH and ORP, as well as conductivity probes, all types of level gauges, temperature probes, and more. Basic components typically generate a signal – usually voltage, current, or resistance – proportional to the variable they measure, such as level, flow, temperature, pressure, or chemical process. The basic element is connected to the input of the field transmitter.

Field transmitters include pressure, temperature, and flow devices. They process the signals generated by the basic elements, first characterizing them in a linear format, then applying engineering unit coefficients, and finally sending them in analog (typically 4-20 mA dc) or digital format (usually some various types of fieldbuses).

Data Support When manufacturing field instruments, the basic components and transmitter (or actuator, in the case of a control valve) are factory calibrated, and calibration information is provided with the equipment. This part of the calibration data is usually lost. When a device is put into service, entering this information into a centralized calibration record should be part of the standard work, not just for efficiency reasons. Centralized storage of calibration information ensures that knowledge remains in the plant even if the team changes.

Analog devices

Analog devices – often referred to as "4 to 20 mA loop" devices – because they send "analog" signals that represent the physical quantities being measured (e.g., temperature). The current they send is proportional to the magnitude of the measured physical quantity (analog), with 4 mA representing the minimum proportional value and 20 mA representing the maximum proportional value.

Although many systems are now digital in some respects, analog devices are still widely used in process manufacturing.

Digital devices

Digital devices convert measured physical quantities into digital signals. Many different digital coding methods are now used in the process industry, including Foundation Fieldbus, Profibus, and HART.

A common view is that fieldbus (digital) field devices do not require calibration. This view is wrong. Although fieldbus signals (whether Foundation, Profibus Fieldbus, or connected HART) provide diagnostic information, they do not provide information about the accuracy of the device or confirm that the device reports the process accurately and precisely.

Control valves

The control valve has an actuator, which also needs to be calibrated to regulate wear and reseal the valve to prevent leakage and the effects of viscosity. If these control valves have not been activated on a regular basis, they are often required to be tested for part of their stroke to ensure that they are working reliably.

Licensing and paperwork

From obtaining permits to documenting and filling out the results, administrative tasks add to the cost and time required to perform even on-site calibrations. As Ian Verhappen, former chair of the Industrial Automation Networks FF (Fieldbus Foundation) user group, explains, "In many cases, it often takes longer than the work itself to get all the necessary paperwork (permits, quarantine, etc.) in order. ”

Calibration documentation challenges

Documenting a calibration means handwriting the date and time, pre-calibration readings, adjusted readings, and other technician observations in the logbook. Not surprisingly, many factories continue to use handwritten calibrations for archival calibrations. However, there are many drawbacks to recording with paper and pen.

First, errors are generated and perpetuated. The data in handwritten records is often illegible or inadequate. For facilities using a computerized maintenance management system (CMMS), the additional time required to manually enter handwritten data, as well as possible errors, must be taken into account.

Changing who you work with

Another challenge in maintaining a calibration program is the change in the object of work.

The 80s of the 20th century saw budget cuts and layoffs. Engineering, maintenance and operations staff were drastically reduced, and a new "lean manufacturing" philosophy began to take root and continues to this day, especially in developed countries.

Smaller teams spend less time on mentoring and on-the-job training, so device- and system-specific knowledge information cannot be successfully transferred from individuals to institutions. As older operators and engineers retire, they also take away their knowledge of equipment and systems.

"Every day at four o'clock in the afternoon, the plant's living dictionaries of knowledge come out the door, and some of them sometimes never come back," said the chief engineer of instrumentation and controls at a large refinery in the Midwest of United States.

At the same time, many facilities still require two engineers to perform a single on-site calibration – one for the transmitter and one for the control system. Commissioning of the FF (Fieldbus Foundation) is expected to require at least two hours of work by two technicians.

How can calibration and documentation be done more efficiently?

Use a multi-function documented calibrator

The new generation of "smaller" on-site calibration tools combines multiple tools to go beyond basic test and measurement, and also provide ancillary analysis and archiving capabilities to greatly improve worker productivity.

The versatile "Documented Process Calibrator" is a handheld, electronic test tool that combines a variety of calibration steps and functions to output, simulate, and measure pressure, temperature, and a wide range of electrical and electronic signals.

Merit:

Engineers have fewer tools to master and carry to the field.

The calibration process and data output for multiple devices are similar compared to using different processes to collect data from each tool and device

Automated steps replace many manual calibration steps

There is no need for a second engineer to document the pre- and post-adjustment status of the field device

Shorter calibration times per device

Calculate the error of a single device, not the sum of the errors of multiple tools

Use a calibration plan

The biggest savings in using a documented calibrator is the integration of the program management tools. The use of a single set of licenses and documentation for full calibration significantly reduces costs.

Implement asset management, calibration management, or computerized maintenance management systems (CMMS)

Unlike paper documents, documented calibrator data is never illegible, ambiguous, or incomplete. The data can be downloaded directly to a variety of CMMS systems without the need to transcribe or fill it in.

Because the documented process calibrator automatically records the pre- and post-adjustment status of each field device, which can be operated by a single technician, the plan-based documented calibrator can save up to 50% of time and cost compared to the traditional manual method of calibrating a single device. In other words, the same lean team can do more than twice as much calibration in a given time period.

Running a lean team under the traditional demands of the job inevitably leads to mistakes. Calibration does not always work as intended. Don't ignore the looming threat and look at how you can do your existing practices more efficiently and cheaply. Implementing plan-based calibration, paperless archiving, and CMMS data management will allow more calibrations to be performed more consistently, and knowledge will be transferred from the individual to the entire team and even the entire organization, resulting in a significant increase in productivity and quality.

Calibrating multiple instruments in a planned sequence reduces the cost per calibration compared to calibrating one instrument at a time.

In addition to savings in maintenance costs, savings in legal costs and lost revenue due to accidents can exceed hundreds of millions of dollars. Good calibration maintenance practices help reduce the likelihood of these events. In the event of a disaster, a good calibration record can be part of the defense evidence in the event of a legal incident in the factory, and similarly, a bad record can put the unit in a very disadvantageous legal position.

5 major calibration test tools

The following recommended calibration tools ensure a streamlined process:

1Fluke 754 Documented Full-Featured Process Calibrator

The HART function and automatic calibration procedure meet the most demanding safety standards.

2Fluke DPCTrack2 Calibration Management Software

Manage instrument calibration records, create calibration plans, print reports, and manage calibrated instruments.

3Fluke 721 High Precision Pressure Calibrator

Dual-isolated sensors, high accuracy, suitable for natural gas regulatory transfer applications.

4Fluke 700G Precision Pressure Gauge Calibrator

High-quality, rugged, high-quality pressure for fast, high-precision test results.

5Fluke 709H Precision Loop Calibrator with HART support

Full-featured precision mA loop calibrator with integrated HART communication function.

Schedule-based workflows help you save money on process instrument maintenance

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